JP2017024366A - Printer and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress discharge failure of ink due to a nozzle.SOLUTION: A printer combines a first scan discharging ink from nozzles in association with movement of a print head after executing first transportation transporting a printing medium to a position where a first boundary switching from a blank area to a non-blank area of an image coincides with an end portion of one end side in a transportation direction of a nozzle array when the printing medium is transported from one end side toward the other end side in the transportation direction of the printing medium intersecting with a main scanning direction and a second scan discharging the ink from the nozzles in association with the movement of the print head after executing second transportation transporting the printing medium to a position where a second boundary switching from the non-blank area to the blank area of the image coincides with an end portion of the other end side in the transportation direction of the nozzle array when the printing medium is transported from one end side toward the other end side in the transportation direction, and prints the image.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a printing apparatus and a printing method.

  Printing an image on a print medium by ejecting ink from each nozzle while moving a print head having a nozzle row in which a plurality of nozzles are arranged in the nozzle row direction in a direction intersecting the nozzle row (scanning of the print head) Inkjet printers that perform this are known.

  In addition, the effective dot of the character pattern is compared with the number of dots that can be recorded by the recording head, and recording is performed for each character pattern whose character pattern size does not exceed the print width of the recording head. There has been proposed a recording apparatus that performs printing without cutting over the boundary line (see Patent Document 1).

JP-A-6-79922

  When recording is performed for each character pattern that does not exceed the print width of the recording head (printing head) as in the above-mentioned document, among the nozzles constituting the nozzle row, nozzles that are used less frequently are easily fixed. . Specifically, among the nozzles constituting the nozzle row, some nozzles located on the downstream side (or upstream side) of the print medium conveyance direction are extremely low in frequency used for printing the character pattern. There is a trend. In a nozzle that is used less frequently, the ink in the nozzle is thickened by drying. Such thickening may cause ink ejection failure (a state where ink is not ejected when ink should be ejected) due to nozzle clogging, and may lead to a decrease in print quality.

  The present invention has been made in view of at least the above-described problems, and provides a printing apparatus and a printing method capable of improving printing quality by suppressing ink ejection defects from nozzles.

  According to one aspect of the present invention, ink is ejected from the nozzles as the print head having a nozzle row in which a plurality of nozzles are arranged in a predetermined nozzle row direction moves in the main scanning direction intersecting the nozzle row. A printing apparatus that prints an image on a print medium, from a blank area of the image to a non-blank area when moving from one end side to the other end side in the transport direction of the print medium that intersects the main scanning direction. After performing the first transport for transporting the printing medium to a position where the first boundary to be switched matches the end of the nozzle row on the one end side in the transport direction, ink is ejected from the nozzles as the print head moves. And a second boundary that switches from a non-blank area to a blank area of the image when moving from one end side to the other end side in the transport direction is the other end side of the nozzle row in the transport direction. End of On executing the second conveyance for conveying the print medium to a position fit to print the image by combining a second scanning for ejecting ink from the nozzles in accordance with the movement of the print head.

  According to this configuration, the nozzle including the nozzle on one end side in the transport direction of the nozzle row is used in the first scan, and the nozzle including the nozzle on the other end side in the transport direction of the nozzle row is used in the second scan. The For this reason, the difference in the use frequency for each nozzle as described above is suppressed, and a decrease in print quality due to ink ejection failure is avoided.

In one aspect of the present invention, in the image, an adjacent region having the same size as the first region adjacent to the other end side in the transport direction is disposed in the first region that can be printed by the nozzle row in the first scan. When defined, the second boundary closest to the other end side in the transport direction among the second boundaries in the adjacent region corresponds to the end of the nozzle row on the other end side in the transport direction. It is also possible to determine a transport amount for two transports and execute the second transport with the transport amount after the first scan.
According to this configuration, after the first scan, it is possible to execute the second transport so that the nozzle on the other end side in the transport direction of the nozzle row is reliably used in the second scan.

One aspect of the present invention is that, in the image, the first boundary on the other end side in the transport direction is the most of the first boundaries in the first region that can be printed by the nozzle row in the first scan. When the second boundary in the first region is located on the other end side in the transport direction more than the second boundary on the other end side in the transport direction, the transport direction in the first region is the most in the transport direction. The region on the one end side in the transport direction from the second boundary on the other end side of the image may be printed by the first scanning.
Further, in the image, the second boundary closest to one end in the transport direction among the second boundaries in the second region that can be printed by the nozzle row in the second scan is the second boundary in the second region. When one boundary is located closer to one end in the transport direction than the first boundary closest to one end in the transport direction, the transport from the first boundary closest to the one end in the transport direction in the second region The area on the other end side in the direction may be printed by the second scanning.
According to these configurations, it is possible to avoid printing a common non-blank area (area where ink is to be ejected) in the image by each of different scans across the conveyance of the print medium.

The first transport and the first scan described above and the second transport and the second scan do not necessarily have to be performed alternately. Accordingly, one of the aspects of the present invention is that when the amount of ink ejected from the predetermined number of nozzles on one end side in the transport direction of the nozzle row by the first scanning is less than or equal to a predetermined threshold value, The first scanning may be repeated after executing the first conveyance.
According to this configuration, when it is difficult to say that the nozzle on one end side in the transport direction of the nozzle row is sufficiently used during the first scan, the one end is performed by performing the first transport and the first scan again. It is possible to appropriately suppress ink thickening at the side nozzle. Similarly, when the amount of ink ejected from the predetermined number of nozzles on the other end side in the transport direction of the nozzle row by the second scan is equal to or smaller than a predetermined threshold value, the second transport is further executed. The second scan may be repeated.

  The technical idea of the present invention is also realized by a device other than a printing device. For example, the present invention is classified into various categories such as a method (printing method) including a step executed by a printing apparatus, a computer program for causing a computer to execute the method, and a computer-readable storage medium storing the program. May be realized.

The block diagram which illustrates the device composition concerning this embodiment. 6 is a flowchart showing print control processing. FIG. 3 is a diagram illustrating a configuration of a print head. The flowchart which illustrates the detail of an output process. The figure which shows an example of print data. The figure which shows an example of the correspondence of a nozzle and a pixel.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each drawing is only an example for explaining an embodiment, and may not be in alignment with each other.

1. Schematic description of the device:
FIG. 1 is a block diagram illustrating functions of the printing apparatus 10 and the like according to the present embodiment. The printing apparatus 10 is grasped as a product such as a printer or a multifunction peripheral including a printer function. The printing apparatus 10 may be called a printing control apparatus, an image processing apparatus, or the like. The printing apparatus 10 is configured to include a printing unit 30 that actually performs printing on a printing medium and a partial configuration (for example, a control unit 11 described later) for controlling the behavior of the printing unit 30. In this case, a part of the configuration may be referred to as a printing device, a printing control device, or the like. Each configuration of the printing apparatus 10 illustrated in FIG. 1 is not limited to a single location or a case where the configurations are integrated in a single case. A system may be constructed. For example, the printing apparatus 10 includes a device (such as a personal computer) that controls a printer by mounting a program (such as a printer driver) for controlling the behavior of a printer that actually performs printing on a print medium. It may be.

  In FIG. 1, the printing apparatus 10 is illustrated as a configuration including a control unit 11, an operation input unit 16, a display unit 17, a communication interface (I / F) 18, a slot unit 19, a printing unit 30, and the like. The control unit 11 includes, for example, an IC having a CPU, a ROM, a RAM, and other storage media. In the control unit 11, various processing (for example, print control processing described later) is realized by the CPU executing arithmetic processing according to a program stored in a ROM or the like using the RAM or the like as a work area. .

  The operation input unit 16 includes various buttons and keys for accepting an operation by the user. The display unit 17 is a part for displaying various information related to the printing apparatus 10 and is configured by, for example, a liquid crystal display (LCD). A part of the operation input unit 16 may be realized as a touch panel displayed on the display unit 17.

  The printing unit 30 is a mechanism for printing an image on a print medium. When the printing method employed by the printing unit 30 is an inkjet method, the printing unit 30 includes a print head 31 (see FIG. 3), a carriage 35 that moves the print head 31 along a predetermined main scanning direction (main scanning), It has a configuration such as a transport unit 36 that transports the print medium along a transport direction that intersects the main scanning direction. The printing unit 30 may be a device that can execute color printing, or may be a device that cannot perform color printing but can perform monochrome printing.

  The print head 31 receives supply of ink from an ink cartridge (not shown). When the printing unit 30 is an apparatus capable of performing color printing as described above, the print head 31 includes a plurality of types of ink (for example, cyan (C) ink, magenta (M) ink, yellow (Y) ink, and black. (K) Ink, etc.) are supplied from various ink cartridges. On the other hand, when the printing unit 30 is an apparatus that performs monochrome printing as described above, the print head 31 receives supply of K ink from an ink cartridge of K ink. The print head 31 can eject (eject) ink (ink droplets) from a plurality of nozzles 34 (see FIG. 3). When the ejected ink lands on the print medium, dots are formed on the print medium and printing is realized. “Dot” basically refers to an ink droplet that has landed on a print medium, but the expression “dot” is also used as appropriate in the description of the process before the ink droplet has landed on the print medium. The specific types and number of liquids used by the printing unit 30 are not limited to those described above. For example, various inks and liquids such as light cyan, light magenta, orange, green, gray, light gray, white, metallic ... It can be used.

  The transport unit 36 includes a roller for supporting and transporting the print medium, a motor for rotating the roller (all not shown), and the like. The rotation of the motor is controlled by the control unit 11. The print medium is typically paper. However, in the present embodiment, materials other than paper are included in the concept of the printing medium as long as the material can record the liquid and can be transported by the transport unit 36.

The communication I / F 18 is a general term for interfaces for connecting the printing apparatus 10 to the external device 100 by wire or wirelessly. Examples of the external device 100 include various devices that are input sources of image data for the printing apparatus 10 such as a smartphone, a tablet terminal, a digital still camera, and a personal computer (PC). The printing apparatus 10 can be connected to the external device 100 via the communication I / F 18 by various means and communication standards such as a USB cable, a wired network, a wireless LAN, and e-mail communication.
The slot part 19 is a part for inserting an external storage medium such as a memory card. That is, the printing apparatus 10 can also input image data stored in the storage medium from an external storage medium such as a memory card inserted into the slot unit 19.

  FIG. 2 is a flowchart showing print control processing executed by the control unit 11. When the control unit 11 inputs a file representing an image to be printed (step S100), the control unit 11 executes image processing for generating print data from the file (step S200). The file input in step S100 is a file generated by various applications, and the format is expressed in gradation (for example, 256 gradations from 0 to 255) in RGB (red, green, blue) for each pixel. There are various types such as bitmap data and text data. The control unit 11 appropriately performs known image processing such as file analysis, character code conversion, resolution conversion, color (color system) conversion, halftone processing, and the like according to the format of the input file. As a result, print data that expresses an image to be printed with a dot pattern (dot pattern) with a plurality of pixels is generated.

  The dot pattern is an array of dots on (dot formation or ink ejection) / off (dot non-formation or ink non-ejection), and it can be said that the dot on / off is defined for each pixel. When the printing unit 30 supports color printing and the print head 31 ejects, for example, CMYK ink, the print data includes data defining dot on / off for each pixel for each CMYK. Yes. On the other hand, when the printing unit 30 is compatible with monochrome printing and the print head 31 discharges K ink, the print data is data that defines on / off of K ink dots for each pixel.

  The control unit 11 determines an assignment destination nozzle 34 for each pixel constituting such print data, and rearranges the print data after a predetermined arrangement for transfer to the print head 31 in accordance with the determination. An output process for transferring to the print head 31 is performed (step S300). By such allocation of each pixel to the nozzle 34, it is determined by which nozzle 34 of the print head 31 the dot of each pixel constituting the print data is formed. In step S300, the control unit 11 also determines the conveyance amount of the print medium and the conveyance instruction (control of the conveyance unit 36) based on the determined conveyance amount. Details of step S300 in the present embodiment will be described later with reference to FIG.

  The print head 31 drives each nozzle 34 based on the transferred print data. For example, it is assumed that a drive signal (a kind of pulse) for driving each nozzle 34 is given to the print head 31 by the control unit 11. Although detailed explanation is omitted, in the print head 31, the application of the drive signal to the drive element provided for each nozzle 34 is switched according to the dot on / off information for each pixel represented by the print data. To do. Thereby, each nozzle 34 realizes ink ejection / non-ejection according to the information of the pixel assigned to itself. As a result, the image to be printed is printed on the print medium.

  FIG. 3 simply illustrates the configuration of the print head 31 and the like. FIG. 3 illustrates the arrangement of the nozzles 34 on the ink ejection surface 31 a of the print head 31 from the viewpoint from above the print head 31. In FIG. 3 (and FIG. 6 described later), the nozzle 34 is indicated by a circle. The ink ejection surface 31a is a surface on which the nozzles 34 are opened, and is a surface facing the print medium S that is transported along the transport direction by the transport unit 36. In FIG. 3, a direction D1 corresponds to the main scanning direction, and a direction D2 corresponds to the transport direction. Basically, the main scanning direction D1 and the transport direction D2 are orthogonal to each other. In FIG. 3, the symbol US indicates the upstream side in the transport direction D2, and the symbol DS indicates the downstream side in the transport direction D2. That is, the transport unit 36 transports the print medium S from the upstream US in the transport direction D2 to the downstream DS.

  In the example of FIG. 3, the print head 31 corresponds to the nozzle row 33C corresponding to the discharge of C ink, the nozzle row 33M corresponding to the discharge of M ink, the nozzle row 33Y corresponding to the discharge of Y ink, and the discharge of the K ink. The nozzle row 33K is provided. In each of the nozzle arrays 33C, 33M, 33Y, and 33K, a plurality of nozzles 34 for ejecting ink of the corresponding color are arranged at a predetermined interval (a constant nozzle pitch NP) in a predetermined nozzle array direction D3.

  The nozzle row direction D3 to which the nozzle row faces intersects the main scanning direction D1. Although depending on the design of the printing unit 30, the nozzle row direction D3 is orthogonal to the main scanning direction D1 or intersects at an oblique angle that is not orthogonal (90 degrees). In the following, for ease of explanation, it is assumed that the nozzle row direction D3 is orthogonal to the main scanning direction D1. Therefore, the nozzle row direction D3 and the transport direction D2 are parallel. In this specification, even when expressions that are originally strictly interpreted as orthogonal, parallel, constant, etc. are used, these do not mean strictly orthogonal, parallel, constant, but in terms of product performance. It also includes an allowable error and an error that may occur during product manufacturing. In addition to being ejected by one nozzle row, the ink of one color may be ejected by, for example, a plurality of nozzle rows arranged so as to be shifted from each other in the nozzle row direction D3.

  The carriage 35 on which the print head 31 is mounted receives power from a carriage motor (not shown) and moves in parallel with the main scanning direction D1. The print head 31 realizes printing by ejecting ink from the nozzles 34 to the print medium S while moving together with the carriage 35. The process in which the print head 31 ejects ink in association with the movement from one end side to the other end side in the main scanning direction D1 or the movement from the other end side to the one end side in the main scanning direction D1 is performed once as “scanning”. Or “path”. In addition, the conveyance of the print medium S performed by the conveyance unit 36 in response to an instruction from the control unit 11 between the end of one pass and the start of the next pass is also referred to as “paper feeding”. According to such a configuration, it can be said that the printing apparatus 10 realizes printing by controlling the print head 31 having a nozzle row in which a plurality of nozzles 34 are arranged in the nozzle row direction D3.

2. Printing with adjustment of carry amount and nozzle range:
FIG. 4 is a flowchart showing an example of the details of step S300 in FIG.
In step S <b> 310, the control unit 11 performs first conveyance control that realizes the first conveyance of the print medium by the conveyance unit 36. The first transport is the end on the one end side in the transport direction D2 of the nozzle row, where the first boundary that switches from the blank area of the image to be printed to the non-blank area when moving from one end side to the other end side in the transport direction D2. This refers to the process of transporting (paper feeding) the print medium to a position that matches the part (nozzle 34 located at the end).

When the downstream DS in the transport direction D2 is called one end side in the transport direction D2, the upstream side US in the transport direction D2 is the other end side in the transport direction D2. Conversely, when the upstream US in the transport direction D2 is called one end side in the transport direction D2, the downstream US in the transport direction D2 is the other end side in the transport direction D2. In the following description, the downstream DS in the transport direction D2 is defined as one end side in the transport direction D2, and the upstream US in the transport direction D2 is defined as the other end side in the transport direction D2.
The blank area corresponds to an area where a portion where ink is not ejected on the printing medium continues to some extent, and the non-blank area corresponds to an area which continues to some extent including a portion where ink is ejected on the printing medium.

  In step S <b> 320, after the first conveyance by the conveyance unit 36, the control unit 11 causes the printing unit 30 to execute a pass (first scan) for ejecting ink from the nozzles 34 as the print head 31 moves. Take control. At this time, the control unit 11 assigns some pixels constituting the print data to the nozzle range of the plurality of nozzles 34 including the nozzle 34 (downstream nozzle) located at the end of the downstream DS in the nozzle row, Ink is ejected from the nozzles 34 belonging to the nozzle range.

  In step S <b> 330, the control unit 11 performs second conveyance control that realizes the second conveyance of the print medium by the conveyance unit 36. In the second conveyance, the second boundary where the non-blank area of the image to be printed is switched from the non-blank area to the blank area when moving from the downstream DS in the conveyance direction D2 to the upstream US is the upstream US in the conveyance direction D2 of the nozzle row. Is a process of transporting (paper feeding) the print medium to a position matching the end of the nozzle (the nozzle 34 positioned at the end).

  In step S <b> 340, after the second transport by the transport unit 36, the control unit 11 causes the printing unit 30 to execute a pass (second scan) in which ink is ejected from the nozzles 34 as the print head 31 moves. Take control. At this time, the control unit 11 assigns some pixels constituting the print data to the nozzle range of the plurality of nozzles 34 including the nozzle 34 (upstream nozzle) located at the end of the upstream US in the nozzle row, Ink is ejected from the nozzles 34 belonging to the nozzle range.

Steps S310 to S340 will be described more specifically with reference to FIGS.
FIG. 5 illustrates a part of the print data KID, and FIG. 6 illustrates an example of a correspondence relationship between the nozzles 34 constituting the nozzle row and the pixels PX (pixels constituting the print data KID) allocated to the nozzles 34. ing. The print data KID is an example of print data generated by the control unit 11 in step S200 (FIG. 2). Here, it is assumed that the data defines the on / off state of K ink dots for each pixel PX. The print data is composed of a plurality of pixels arranged corresponding to the main scanning direction D1 and the transport direction D2, respectively. For convenience of explanation, the direction of the arrangement of the pixels PX constituting the print data KID may be expressed by the directions D1 and D2, but this is only the direction of the image and the directions D1 and D2 when the printing unit 30 executes printing. Based on the correspondence (match) relationship. Note that in FIG. 5, a rectangle representing each pixel PX illustrated in FIG. 6 is omitted.

  FIG. 6 illustrates a nozzle row 33K that ejects ink (K ink) of a color corresponding to the print data KID among a plurality of nozzle rows of the print head 31. In FIG. 6, for the purpose of simplifying the illustration, the number of nozzles 34 constituting the nozzle row corresponding to one ink color is, for example, 19. In FIG. 6, the numbers # 1 to # 19 assigned to the nozzles 34 are nozzle numbers. That is, for convenience of explanation, nozzle numbers # 1 to # 19 are assigned to the nozzles 34 arranged from one end side in the nozzle row direction D3 (downstream DS in the transport direction D2) to the other end side (upstream US in the transport direction D2). They are attached in order. In FIG. 6, the nozzle 34 with nozzle number # 1 present in the most downstream DS corresponds to the downstream nozzle, and the nozzle 34 with nozzle number # 19 present in the most upstream US corresponds to the upstream nozzle.

  In the example of FIG. 5, the print data KID represents at least an object including a character string described as “ABC...”, A character string described as “DEF...”, A character string described as “GHI. (Each character string is expressed by a dot pattern of K ink). The print data KID shown in FIG. 6 is the same data as the print data KID shown in FIG. 5, but such specific character string notation is omitted in FIG. 6. In any case, the print data KID expresses such character strings by arranging pixels PX having information indicating either dot on or dot off of K ink in a matrix.

  FIG. 6 shows an allocation relationship between the nozzles 34 and the pixels PX when the printing unit 30 employs band printing as a printing method. In FIG. 6, the number (any one of 1 to 19) indicated in the rectangle representing the pixel PX is the nozzle number of the nozzle 34 to which the pixel PX is assigned. In general, band printing means printing a bundle (band) of raster lines for 34 nozzles constituting the nozzle range included in the nozzle row in one pass of the print head 31. This is a printing method in which paper feeding and paper feeding are alternately repeated. A raster line is an area expressed by a set (also referred to as a pixel row) of a plurality of pixels PX continuous along the main scanning direction D1, and basically forms one raster line in band printing. The pixel PX is assigned to one common nozzle 34 and printed. Of course, the printing method that can be adopted by the printing unit 30 is not limited to band printing. However, in any printing method, the control unit 11 determines which pixels constituting the printing data should be assigned to which nozzles 34. It can be recognized and determined according to the printing method.

  In FIG. 6, the position of the nozzle row 33K (print data KID in the transport direction D2) for each pass by the print head 31 (the first pass, the second pass, the third pass ... for one print medium). It also shows that the relative position) changes. Of course, the print head 31 does not actually move to the upstream side US along the transport direction D2, but the print medium is fed to the downstream side DS in the transport direction D2 by the transport unit 36 every time the pass is completed. Information on the pixel PX relating to the band to be printed in the next pass is assigned to the nozzle 34.

  In step S310, the control unit 11 detects the most downstream DS at the present time among the first boundaries where the blank area of the image to be printed is switched from the blank area to the non-blank area when moving from the downstream DS in the transport direction D2 to the upstream US. The first boundary of is specified. Here, in the vicinity of the print data KID in FIGS. 5 and 6, a symbol “T (True)” or “F (False)” is assigned for each raster line for convenience. This is a flag indicating the presence of a raster line having dots. A raster line with “T”, that is, a flag, includes one or more dot-on pixels PX, and a raster line that has “F”, that is, without a flag, does not include a dot-on pixel PX. The control unit 11 can set the flag as described above for each raster line of the print data KID, and can specify the first boundary and the second boundary according to the flag. The control unit 11 regards the raster line with the flag as a part of the non-blank area, and regards the raster line without the flag as a part of the blank area. In addition, the control unit 11 regards the raster line with the flag adjacent to the raster line without the flag as the first boundary or the second boundary.

  That is, the control unit 11 searches for a flag for each raster line from the downstream DS in the transport direction D2 toward the upstream US, and determines the raster line with the flag when the flag is switched from without flag to the first boundary. Identified as one of the following. In addition, by the search, the raster line with the flag when the flag is switched to the flag without is specified as one of the second boundaries. With this process, for example, in the case of the first transport control performed before the first pass (one of the first scans), the control unit 11 can control the most downstream DS included in the print data KID. The raster line (see reference numeral BL11 in FIGS. 5 and 6) corresponding to the end of the downstream DS of the character string “ABC...” That is the object is identified as the first boundary of the most downstream DS at the present time. .

  Then, the control unit 11 determines the transport amount necessary for transporting the print medium to the position where the raster line as the first boundary specified in this way is printed by the downstream nozzle, and the transport unit 36 The print medium is fed to the downstream DS in the transport direction D2 by the determined transport amount. For example, in the case of the first transport control performed before the first pass (one of the first scans), the control unit 11 has the end facing the downstream DS of the print medium downstream of the downstream nozzle. The print medium is fed to a position that passes a predetermined distance to the side DS. The predetermined distance referred to here is the width of the downstream DS margin determined in advance by print settings and the like along the conveyance direction D2 from the downstream DS end of the print data KID to the raster line as the boundary BL11. The distance is the sum of the distance (the actual distance converted based on the number of pixels along the transport direction D2 and the size of one pixel).

  In step S320, the control unit 11 most upstream of the conveyance direction D2 among the first boundaries in the area (first area) that can be printed by the nozzle row in the first scan executed in step S320 in the image to be printed. When the first boundary of the side US is located upstream of the second boundary of the most upstream US among the second boundaries in the first region, the first boundary of the most upstream US in the first region The region from the second boundary to the downstream DS is printed by the first scan executed in step S320.

  5 and 6, for example, the first area that can be printed by the nozzle row 33K in the first pass (one of the first scans) is that the raster line as the boundary BL11 is the most downstream DS. This is a region corresponding to a bundle of 19 raster lines indicated by reference numeral BD1. That is, if all nozzles 34 of nozzle numbers # 1 to # 19 are used in the first pass, the region BD1 can be printed. In addition to the boundary BL11 described above, the first boundary in the area BD1 is described as a raster line corresponding to the end of the downstream DS of the character string described as “DEF...” (See reference numeral BL12), “GHI. Raster line corresponding to the end of the downstream DS of the character string (see reference numeral BL13) and the raster line corresponding to the end of the downstream DS of the character string described as "JKL ..." (refer to reference numeral BL14) It is. The second boundary in the region BD1 is a raster line (see reference numeral BL21) corresponding to the upstream US end of the character string “ABC...” And a character string “DEF. A raster line corresponding to the end of the upstream US (see reference BL22) and a raster line corresponding to the end of the upstream US of the character string “GHI...” (See reference BL23).

  Among such first boundaries (boundaries BL11, BL12, BL13, BL14) in the region BD1, the boundary BL14 on the most upstream side US is the most upstream among the second boundaries (boundaries BL21, BL22, BL23) in the region BD1. Located on the upstream side US from the boundary BL23 of the side US. Therefore, in the first pass (one of the first scans), the control unit 11 detects the region from the most upstream US boundary BL23 to the downstream DS in the region BD1, that is, from the raster line as the boundary BL11. The area up to the raster line as the boundary BL23 is printed. As illustrated in FIG. 6, if the number of raster lines between the boundaries including the boundaries BL11 and BL23 is 16, in the first pass (one of the first scans), the downstream side in the nozzle row 33K. Each pixel PX of the raster line (one band) between the boundaries including the boundaries BL11 and BL23 is assigned to the nozzle range (nozzle ranges of nozzle numbers # 1 to # 16) of the 16 nozzles 34 of DS.

  For example, the control unit 11 can realize allocation (data transfer to the print head 31) of the pixels P constituting the print data KID to the nozzles 34 using the buffer 12 (FIG. 1). it can. The buffer 12 is, for example, a buffer having a capacity capable of temporarily storing print data corresponding to an image area that can be printed in one pass of the print head 31, and the control unit 11 generates a buffer 12 for the generated print data. Write to the buffer and read print data from the buffer 12 repeatedly.

  In the first scan control for the first pass (one of the first scans), the control unit 11 uses the buffer 12 to print the raster line of the most downstream DS to be printed at that time (the raster as the boundary BL11). A read start point is set for the data related to (line), and a read end point is set for the data related to the raster line on the most upstream side US (the raster line as the boundary BL23) to be printed at that time. Then, data relating to each raster line from the start point to the end point is read out, and transferred to the print head 31 in association with (assigned to) the nozzles 34 in the nozzle range to be used at that time. In the case of the first scan control for the first pass (one of the first scans), the control unit 11 uses the downstream DS as a reference for the association. That is, the raster line (the raster line as the boundary BL11) in which the start point is set is associated with the downstream nozzle (nozzle 34 with the nozzle number # 1), and the other raster lines are also associated with the nozzles 34 in order. By such processing, according to FIGS. 5 and 6, in the first pass (one of the first scans), the 16 nozzles 34 (nozzle numbers # 1 to # 1) in the downstream DS of the nozzle row 33K. 16), the character string described as “ABC...”, The character string described as “DEF...”, And the character string described as “GHI.

  In step S330, the control unit 11 first defines an adjacent area having the same size as the first area adjacent to the upstream US with respect to the first area that can be printed by the nozzle row in the first scan (step S320). To do. 5 and 6, when the adjacent area is defined for the first area (area BD1) that can be printed by the nozzle row 33K in the first pass, 19 raster lines having the same size as the area BD1 are defined. An area indicated by a symbol TBD corresponding to a bundle can be defined. Next, in the control unit 11, the second boundary of the most upstream US among the second boundaries in the adjacent region (for example, the adjacent region TBD) matches the end (upstream nozzle) of the upstream US of the nozzle row. Therefore, the transport amount necessary for this is determined, and the transport unit 36 is caused to feed the print medium to the downstream DS in the transport direction D2 by the determined transport amount.

  Referring to FIG. 5, the second boundary in the adjacent region TBD is a raster line (see reference numeral BL24) corresponding to the upstream US end of the character string “JKL...”, “MNO. Raster line corresponding to the upstream US end of the character string described (see reference numeral BL25), and raster line corresponding to the upstream US end of the character string described as "PQR ..." (refer to reference numeral BL26) ). Among these, the second boundary on the most upstream side US is a raster line as the boundary BL26. Accordingly, if the second transport control is performed before the second pass (one of the second scans), the control unit 11 determines that the upstream side nozzle (nozzle number ##) when the first pass is completed. 19 from the raster line at the position corresponding to the nozzle 34) (the raster line of the most upstream US included in the region BD1) to the second boundary (the raster line as the boundary BL26) of the most upstream US in the adjacent region TBD. The print medium may be fed by a distance along the transport direction D2.

  In step S340, the control unit 11 most downstream in the transport direction D2 among the second boundaries in the area (second area) that can be printed by the nozzle row in the second scan executed in step S340 in the image to be printed. When the second boundary of the DS is located downstream of the first boundary of the most downstream DS among the first boundaries in the second region, the second boundary of the most downstream DS in the second region. The region from the first boundary to the upstream US is printed by the second scan executed in step S340.

  5 and 6, for example, the second area that can be printed by the nozzle row 33K in the second pass (one of the second scans) has the raster line as the boundary BL26 at the most upstream side US. This is a region corresponding to a bundle of 19 raster lines indicated by reference numeral BD2. That is, if all the nozzles 34 having nozzle numbers # 1 to # 19 are used in the second pass, the region BD2 can be printed. The second boundaries in the region BD2 are the aforementioned boundaries BL23, BL24, BL25, BL26. In addition to the boundary BL14, the first boundary in the region BD2 is a raster line (see reference numeral BL15) corresponding to the end of the downstream DS of the character string “MNO...” And “PQR. The raster line corresponding to the end portion of the downstream side DS of the character string "" (see reference numeral BL16).

  Among the second boundaries (boundaries BL23, BL24, BL25, BL26) in the region BD2, the most downstream DS boundary BL23 is the most downstream among the first boundaries (boundaries BL14, BL15, BL16) in the region BD2. It exists in the downstream DS from the boundary BL14 of the side DS. Therefore, in the second pass (one of the second scans), the control unit 11 performs the region from the most downstream DS boundary BL14 to the upstream US region in the region BD2, that is, from the raster line as the boundary BL26. The area up to the raster line as the boundary BL14 is printed. As illustrated in FIG. 6, when the number of raster lines between the boundaries including the boundaries BL14 and BL26 is 16, in the second pass (one of the second scans), the upstream side in the nozzle row 33K. Each pixel PX on a raster line (one band) between the boundaries including the boundaries BL14 and BL26 is assigned to a nozzle range (nozzle ranges of nozzle numbers # 4 to # 19) of 16 DS nozzles 34 of DS.

  Also in this case, the control unit 11 uses the buffer 12 to realize allocation of the pixels P constituting the print data KID to the nozzles 34 (data transfer to the print head 31). In the second scan control for the second pass (one of the second scans), the control unit 11 uses the buffer 12 to print the raster line of the most downstream DS to be printed (raster as the boundary BL14). A read start point is set for data relating to (line), and a read end point is set for data relating to the raster line on the most upstream side US (the raster line as the boundary BL26) to be printed at that time. Then, data relating to each raster line from the start point to the end point is read out, and transferred to the print head 31 in association with (assigned to) the nozzles 34 in the nozzle range to be used at that time. In the case of the second scan control for the second pass (one of the second scans), the control unit 11 uses the upstream DS as a reference for the association. That is, the raster line (the raster line as the boundary BL26) in which the end point is set is associated with the upstream nozzle (nozzle # 19), and the other raster lines are also associated with the nozzles 34 in order. According to such processing, according to FIGS. 5 and 6, in the second pass (one of the second scans), the 16 nozzles 34 (nozzle numbers # 4 to ##) on the upstream side US of the nozzle row 33K. 19), the character string described as “JKL...”, The character string described as “MNO...”, And the character string described as “PQR.

  The control unit 11 repeatedly executes the above-described one cycle of steps S310 to S340 until printing on one print medium is basically completed. In other words, when attention is paid to the relationship between the first pass and the second pass, the first pass corresponds to the first scan, the second pass corresponds to the second scan, and the third pass after that. When attention is paid to the relationship between the fourth pass and the fourth pass, the third pass corresponds to the first scan, and the fourth pass corresponds to the second scan. The same relationship holds true for the fifth, sixth, and subsequent paths. For example, in step S310 in the next one cycle after finishing the second pass, the control unit 11 prints the first boundary of the most downstream DS at the present time (according to the examples of FIGS. A raster line as a boundary BL17 corresponding to the end portion of the downstream DS of the character string described as “STU. Then, the control unit 11 performs conveyance necessary for conveying the print medium to a position where the specified first boundary (raster line as the boundary BL17) is printed by the downstream nozzle (nozzle 34 of nozzle number # 1). It is only necessary to determine the amount and cause the transport unit 36 to feed the print medium to the downstream DS in the transport direction D2 by the determined transport amount.

  As described above, according to the present embodiment, the printing apparatus 10 prints an image by combining the execution of the first conveyance and the first scan described above and the execution of the second conveyance and the second scan described above. Thereby, the nozzle range including the downstream nozzles in the nozzle row and the nozzle range including the upstream nozzles are used alternately (every other pass), for example, and the difference in usage frequency for each nozzle 34 is suppressed. Is done. Accordingly, the ejection failure due to the ink thickening as described above hardly occurs in any of the nozzles 34, and the print quality is improved.

  As is known, the printing apparatus 10 can perform a recovery process to eliminate nozzle ejection defects. The recovery process is, for example, flushing of the nozzle 34. The printing apparatus 10 eliminates clogging of the nozzles 34 due to ink thickening or the like (eliminates ejection defects) by flushing that performs ink ejection unrelated to printing of an image to be printed at a predetermined timing. Can do. However, such flushing causes dots that are not related to the image to be printed to be formed on the print medium and consumes ink that is not related to the image to be printed. According to the present embodiment, since it is difficult for ink ejection defects to occur in any of the nozzles 34, the necessity for such a recovery process is reduced. Accordingly, it is possible to avoid as much as possible the disadvantages such as image quality degradation and ink consumption associated with the recovery process (flushing).

  Further, according to the present embodiment, a common non-blank area in an image is not printed in each of different passes (first scan and second scan) across the conveyance of the print medium. According to the examples of FIGS. 5 and 6, in the first pass, the printable area BD1 includes a part of the character string described as “JKL...” But the character string is not printed. The entire character string is printed in the second pass. In the second pass, the printable area BD2 includes a part of the character string described as “GHI...”, But the character string is not printed. The entire string is printed. With such a configuration, it is possible to improve the print quality of characters in which deterioration (shaking of lines) is easily visually recognized, particularly when printing is performed in different passes sandwiching the conveyance of the print medium.

3. Variations:
The present invention is not limited to the above-described embodiment, and can be carried out in various modes without departing from the gist thereof. For example, the following modifications can be adopted. A configuration in which the above-described embodiments and modifications are appropriately combined also falls within the disclosure scope of the present invention. In the description of the following modified examples, the description of matters common to the above-described embodiment will be omitted as appropriate.

<< Modification 1 >>
The first transport and the first scan described above and the second transport and the second scan described above are not necessarily executed alternately. That is, the control unit 11 may irregularly change the execution order of steps S310 and S320 and steps S330 and S340. As an example, as a result of the first scanning control (step S320), the control unit 11 determines that the amount of ink ejected by a predetermined number of nozzles 34 on one end side (downstream DS) in the nozzle row transport direction D2 is a predetermined threshold. If the value is equal to or smaller than the value, the first scanning may be repeated after further executing the first conveyance. For example, in the first pass, the control unit 11 ejects based on print data to which downstream nozzles and neighboring nozzles (for example, three nozzles 34 having nozzle numbers # 1 to # 3) are assigned. If the total number of dots is equal to or less than the predetermined threshold value, it is determined that the use of each nozzle 34 on the downstream DS is insufficient, and the first transport control (step S330) is performed again instead of the second transport control (step S330). Step S310) is executed.

  The control unit 11 may estimate the total number of such dots by analyzing the print data (determined by calculation), or by actually analyzing the vibration of the drive element that ejects ink from the nozzles 34 or the like. The number of hits may be counted. In the second first transport control (step S310), the control unit 11 reads the first boundary of the most downstream DS at the present time (for example, “JKL...” Not printed in the first pass) The raster line as the boundary BL14 corresponding to the end of the downstream side DS of the row feeds the print medium to a position where printing is performed by the downstream side nozzle (nozzle 34 of nozzle number # 1). And the control part 11 performs 1st scanning control (step S320) in such a state, and implement | achieves a 2nd path | pass.

  As a result, the above-described downstream nozzle and the neighboring nozzles are sufficiently used by the first pass and the second pass. That is, the control unit 11 can perform control so that both the first pass and the second pass correspond to the first scan. Of course, the control unit 11 may perform control so that both the subsequent third pass and the fourth pass correspond to the second scan (repeat steps S330 and S340 twice). According to such a modification, the order of execution of steps S310 and S320 and steps S330 and S340 is irregularized according to the amount of ink ejected by the nozzles 34 (not necessarily executed alternately). In some cases, it is possible to effectively suppress variation in the usage frequency for each of the 34.

<< Modification 2 >>
In the description with reference to FIGS. 5 and 6, attention is paid to the K ink (the nozzle row 33 that discharges the K ink and the print data KID related to the K ink), but the same description can be made using other colors of ink CMY. can do. However, on the premise of color printing using nozzle rows 33C, 33M, 33Y, and 33K using CMYK ink, the raster line corresponding to the blank area ("F", ie, the raster line without flag) is all CMYK ink. It is assumed that the raster line is composed of only pixels PX whose dots are off. Alternatively, the raster line corresponding to the blank area may indicate a raster line in which the number of dot-ons is equal to or less than a threshold value that is the total of CMYK inks. A raster line corresponding to a non-blank area (“T”, that is, a raster line with a flag) refers to a raster line other than a raster line corresponding to a blank area anyway.

<< Modification 3 >>
The printing method employed by the printing unit 30 is not limited to the band printing described above. For example, the printing unit 30 may employ pseudo band printing as a printing method. Pseudo band printing is also referred to as microfeed (MF) printing. The pseudo band printing is roughly performed in the transport direction D2 by performing a plurality of passes with a paper feed (minute feed) of a distance shorter than the nozzle pitch NP as compared with the band printing by one pass. A high-resolution area (pseudo band) is printed, and printing of such a pseudo band and paper feeding of a relatively long distance of the printing medium (paper feeding substantially equivalent to the first conveyance and the second conveyance) are alternately performed. This is a printing method repeated repeatedly. Specifically, the control unit 11 executes the first pass, the minute feed, and the second pass after the first transfer, and executes the second transfer between the second pass and the third pass. Then, the third pass, the minute feed, and the fourth pass are executed, and one cycle control such as... Can be repeatedly performed. In this case, the combination of two passes before and after the minute feed (the combination of the first and second passes, the combination of the third and fourth passes) corresponds to either the first scan or the second scan. become.

<< Modification 4 >>
The downstream nozzle and the upstream nozzle described above are not necessarily nozzles that exist strictly at both ends in the nozzle row. For example, the nozzle row may have a predetermined number of nozzles, which are called spare nozzles and are not normally used for ink ejection, in each of the downstream DS and the upstream US. In such a case, the nozzles existing at both ends among the nozzles excluding the spare nozzle in the nozzle row can be handled as the downstream nozzle and the upstream nozzle.

DESCRIPTION OF SYMBOLS 10 ... Printing apparatus, 11 ... Control part, 12 ... Buffer, 30 ... Printing part, 31 ... Print head, 33C, 33M, 33Y, 33K ... Nozzle row, 34 ... Nozzle, 35 ... Carriage, 36 ... Conveying part, 100 ... External device, KID ... print data, S ... print medium

Claims (6)

An image is printed on a print medium by ejecting ink from the nozzle in accordance with the movement in the main scanning direction intersecting the nozzle row of a print head having a nozzle row in which a plurality of nozzles are arranged in a predetermined nozzle row direction. A printing device,
A first boundary that switches from a blank area of the image to a non-blank area when the print medium crosses the main scanning direction from one end side to the other end side in the transport direction is one end of the nozzle row in the transport direction. A first scan for ejecting ink from the nozzles along with the movement of the print head after performing the first transport for transporting the print medium to a position that matches the end of the side;
When the second boundary where the non-blank area of the image is switched from the non-blank area to the blank area when moving from one end side to the other end side in the transport direction is aligned with the end of the nozzle row on the other end side in the transport direction. A second scan for ejecting ink from the nozzle as the print head moves after performing a second transport for transporting the print medium;
A printing apparatus that prints the image in combination.   In the image, when an adjacent area of the same size as the first area adjacent to the other end side in the transport direction is defined in the first area that can be printed by the nozzle row in the first scan, Determining the transport amount of the second transport necessary for the second boundary on the other end side in the transport direction of the second boundary to be aligned with the end of the nozzle row on the other end side in the transport direction; The printing apparatus according to claim 1, wherein after the first scan, the second conveyance is performed based on the conveyance amount.   In the image, the first boundary on the other end side in the transport direction among the first boundaries in the first area that can be printed by the nozzle row in the first scan is the second boundary in the first area. When the boundary is located on the other end side in the transport direction more than the second boundary on the other end side in the transport direction, from the second boundary on the other end side in the transport direction in the first area. The printing apparatus according to claim 1, wherein an area on one end side in the transport direction is printed by the first scanning.   In the image, the second boundary closest to one end in the transport direction among the second boundaries in the second region that can be printed by the nozzle row in the second scan is the first boundary in the second region. Of the second region in the transport direction from the first boundary on the one end side in the transport direction in the second region. The printing apparatus according to claim 1, wherein an area on the other end side is printed by the second scanning.   When the amount of ink ejected from a predetermined number of nozzles on one end side in the transport direction of the nozzle row by the first scan is less than or equal to a predetermined threshold value, the first transport is further performed and the first transport is performed. The printing apparatus according to claim 1, wherein scanning is repeated. An image is printed on a print medium by ejecting ink from the nozzle in accordance with the movement in the main scanning direction intersecting the nozzle row of a print head having a nozzle row in which a plurality of nozzles are arranged in a predetermined nozzle row direction. Printing method,
A first boundary that switches from a blank area of the image to a non-blank area when the print medium crosses the main scanning direction from one end side to the other end side in the transport direction is one end of the nozzle row in the transport direction. A first scan for ejecting ink from the nozzles along with the movement of the print head after performing the first transport for transporting the print medium to a position that matches the end of the side;
When the second boundary where the non-blank area of the image is switched from the non-blank area to the blank area when moving from one end side to the other end side in the transport direction is aligned with the end of the nozzle row on the other end side in the transport direction. A second scan for ejecting ink from the nozzle as the print head moves after performing a second transport for transporting the print medium;
A printing method characterized by printing the image in combination.

Images